1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2001 Sistina Software (UK) Limited
4 *
5 * This file is released under the GPL.
6 */
7
8 #include "dm-core.h"
9
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/kmod.h>
13 #include <linux/bio.h>
14 #include <linux/dax.h>
15
16 #define DM_MSG_PREFIX "target"
17
18 static LIST_HEAD(_targets);
19 static DECLARE_RWSEM(_lock);
20
__find_target_type(const char * name)21 static inline struct target_type *__find_target_type(const char *name)
22 {
23 struct target_type *tt;
24
25 list_for_each_entry(tt, &_targets, list)
26 if (!strcmp(name, tt->name))
27 return tt;
28
29 return NULL;
30 }
31
get_target_type(const char * name)32 static struct target_type *get_target_type(const char *name)
33 {
34 struct target_type *tt;
35
36 down_read(&_lock);
37
38 tt = __find_target_type(name);
39 if (tt && !try_module_get(tt->module))
40 tt = NULL;
41
42 up_read(&_lock);
43 return tt;
44 }
45
load_module(const char * name)46 static void load_module(const char *name)
47 {
48 request_module("dm-%s", name);
49 }
50
dm_get_target_type(const char * name)51 struct target_type *dm_get_target_type(const char *name)
52 {
53 struct target_type *tt = get_target_type(name);
54
55 if (!tt) {
56 load_module(name);
57 tt = get_target_type(name);
58 }
59
60 return tt;
61 }
62
dm_put_target_type(struct target_type * tt)63 void dm_put_target_type(struct target_type *tt)
64 {
65 down_read(&_lock);
66 module_put(tt->module);
67 up_read(&_lock);
68 }
69
dm_target_iterate(void (* iter_func)(struct target_type * tt,void * param),void * param)70 int dm_target_iterate(void (*iter_func)(struct target_type *tt,
71 void *param), void *param)
72 {
73 struct target_type *tt;
74
75 down_read(&_lock);
76 list_for_each_entry(tt, &_targets, list)
77 iter_func(tt, param);
78 up_read(&_lock);
79
80 return 0;
81 }
82
dm_register_target(struct target_type * tt)83 int dm_register_target(struct target_type *tt)
84 {
85 int rv = 0;
86
87 down_write(&_lock);
88 if (__find_target_type(tt->name)) {
89 DMERR("%s: '%s' target already registered",
90 __func__, tt->name);
91 rv = -EEXIST;
92 } else {
93 list_add(&tt->list, &_targets);
94 }
95 up_write(&_lock);
96
97 return rv;
98 }
99 EXPORT_SYMBOL(dm_register_target);
100
dm_unregister_target(struct target_type * tt)101 void dm_unregister_target(struct target_type *tt)
102 {
103 down_write(&_lock);
104 if (!__find_target_type(tt->name)) {
105 DMCRIT("Unregistering unrecognised target: %s", tt->name);
106 BUG();
107 }
108
109 list_del(&tt->list);
110
111 up_write(&_lock);
112 }
113 EXPORT_SYMBOL(dm_unregister_target);
114
115 /*
116 * io-err: always fails an io, useful for bringing
117 * up LVs that have holes in them.
118 */
io_err_ctr(struct dm_target * tt,unsigned int argc,char ** args)119 static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
120 {
121 /*
122 * Return error for discards instead of -EOPNOTSUPP
123 */
124 tt->num_discard_bios = 1;
125 tt->discards_supported = true;
126
127 return 0;
128 }
129
io_err_dtr(struct dm_target * tt)130 static void io_err_dtr(struct dm_target *tt)
131 {
132 /* empty */
133 }
134
io_err_map(struct dm_target * tt,struct bio * bio)135 static int io_err_map(struct dm_target *tt, struct bio *bio)
136 {
137 return DM_MAPIO_KILL;
138 }
139
io_err_clone_and_map_rq(struct dm_target * ti,struct request * rq,union map_info * map_context,struct request ** clone)140 static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
141 union map_info *map_context,
142 struct request **clone)
143 {
144 return DM_MAPIO_KILL;
145 }
146
io_err_release_clone_rq(struct request * clone,union map_info * map_context)147 static void io_err_release_clone_rq(struct request *clone,
148 union map_info *map_context)
149 {
150 }
151
io_err_io_hints(struct dm_target * ti,struct queue_limits * limits)152 static void io_err_io_hints(struct dm_target *ti, struct queue_limits *limits)
153 {
154 limits->max_discard_sectors = UINT_MAX;
155 limits->max_hw_discard_sectors = UINT_MAX;
156 limits->discard_granularity = 512;
157 }
158
io_err_dax_direct_access(struct dm_target * ti,pgoff_t pgoff,long nr_pages,enum dax_access_mode mode,void ** kaddr,pfn_t * pfn)159 static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
160 long nr_pages, enum dax_access_mode mode, void **kaddr,
161 pfn_t *pfn)
162 {
163 return -EIO;
164 }
165
166 static struct target_type error_target = {
167 .name = "error",
168 .version = {1, 6, 0},
169 .features = DM_TARGET_WILDCARD,
170 .ctr = io_err_ctr,
171 .dtr = io_err_dtr,
172 .map = io_err_map,
173 .clone_and_map_rq = io_err_clone_and_map_rq,
174 .release_clone_rq = io_err_release_clone_rq,
175 .io_hints = io_err_io_hints,
176 .direct_access = io_err_dax_direct_access,
177 };
178
dm_target_init(void)179 int __init dm_target_init(void)
180 {
181 return dm_register_target(&error_target);
182 }
183
dm_target_exit(void)184 void dm_target_exit(void)
185 {
186 dm_unregister_target(&error_target);
187 }
188